Treating webs which comprise meltable components with thermal energy is well known in the art, both for bonding such webs and/or creating apertures in such webs, such as by running webs through a nip of two rolls, one or both of which may be heated and/or embossed. This principle can be applied to consolidating webs as such, such as non-woven webs, or by connecting webs to each other, such as creating a seam-like bond.
For example, businesses in the textile and personal products industries often manufacture articles such as diapers, clothing, etc., that are ultrasonically welded.
U.S. Pat. No. 6,457,626 (Branson) describes the use of a rotary anvil and a rotary horn comprising two symmetrical halves, for ultrasonic welding of diapers, clothing in textile and personal products industries and film sealing industries. U.S. Pat. No. 6,517,651 (Tefron) describes a stationary ultrasonic horn cooperating with a rotating anvil. U.S. Pat. No. 6,517,650 (Kimberly-Clark) pertains to apparatus and methods for intermittently creating ultrasonic bonds in sequentially advancing work piece segments in a nip. The apparatus is designed sufficiently rigid, that the ultrasonic horn and the anvil can be brought together with low interference levels.
In EP1144187A1 a process is described, wherein circular protrusion on a bonding roll create circular bond points exhibiting a particular three-dimensional cross-section. However, the construction of such a roll as well as its operation is difficult and the circular bond points do not allow for directional property differences in the material.
In WO2008/129138 individual bonding points are shown having the shape of oval perimeter aligned in machine respectively cross-machine direction. According to the description it improves the abrasion resistance without compromising softness and drapeability.
WO99/014415 discloses a bonding pattern for a web showing oval bonding points arranged in a skewed angle relative to the machine direction. In WO09/021,473 (PEGAS) a bonding pattern is described with machine directionally extending bonding points. On the bonding roll, the bonding point protrusions have an oval shape and a trapezoidal cross-section. In U.S. Pat. No. 6,713,159 (K-C) a seaming pattern comprising oval bonding points is described. U.S. Pat. No. 6,220,490 (K-C) discloses a seaming pattern with at least two sub-patterns for specific distribution of stress forces across the seam. In U.S. Pat. No. 5,620,779 relating to creating ribboned non-woven, bonding patterns are described which comprise ovals and/or ellipses as well as skewing of bonding pattern relative to the machine direction.
It is also known to employ ultrasonics for the creation of apertures in web materials, such as described in U.S. Pat. No. 3,949,127 or U.S. Pat. No. 3,966,519, relating to nonwoven materials, or U.S. Pat. No. 3,756,880 relating to films.
It is characteristic of such known methods, that the total system of energy emitting source (e.g. sonotrode) and counteracting anvil is designed very stiff and rigid, as it is believed that flexibility in the system induces inaccuracy and is influencing the energy transmission.